A radical on the Met-Tyr-Trp modification required for catalase activity in catalase-peroxidase is established by isotopic labeling and site-directed mutagenesis.

ABSTRACT: A transient tyrosyl-like radical with a narrow doublet X-band EPR signal is present during catalase turnover by Mycobacterium tuberculosis catalase-peroxidase (KatG). Labeling of KatG with beta-methylene-deuterated tyrosine causes a collapse of the doublet to a singlet, while for 3,5-ring-deuterated tyrosine-labeled enzyme, no changes occur in the EPR signal. Except for the replacement Tyr229Phe, all other single-tyrosine mutants of KatG exhibit the same narrow doublet EPR signal and catalase activity similar to that of the wild-type enzyme. These findings confirm that this catalytically competent radical is associated with Tyr229, whose 3' and 5' protons are replaced as a result of cross-links with neighboring Met255 and Trp107 side chains in the post-translationally modified enzyme conta

SUBMITTER: Zhao X 

PROVIDER: S-EPMC2897066 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature